Fast protein separation by reversed-phase high-performance liquid chromatography on octadecylsilyl-bonded non-porous silica gel

Preparation of N-doped carbon quantum dots for highly sensitive detection of dopamine by an electrochemical method

The glass carbon electrode modified by N-doped carbon quantum dots (NCQD) (NCQD/GCE) has been used to detect dopamine (DA) with broad linear range and low detection limit.

High Sequence Coverage of Proteins Isolated from Liquid Separations of Breast Cancer Cells Using Capillary Electrophoresis-Time-of-Flight MS and MALDI-TOF MS Mapping

A method has been developed for high sequence coverage analysis of proteins isolated from breast cancer cell lines. Intact proteins are isolated using multidimensional liquid-phase separations that permit the collection of individual protein fractions. Protein digests are then analyzed by both matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) peptide mass fingerprinting and by capillary electrophoresis-electrospray ionization (CE-ESI)-TOF MS peptide mapping. These methods can be readily interfaced to the relatively clean proteins resulting from liquid-phase fractionation of cell lysates with little sample preparation. Using combined sequence information provided by both mapping methods, 100% sequence coverage is often obtained for smaller proteins, while for larger proteins up to 75 kDa, over 90% coverage can be obtained. Furthermore, an accurate intact protein MW value (within 150 ppm) can be obtained from ESI-TOF MS. The intact MW together with high coverage sequence information provides accurate identification. More notably the high sequence coverage of CE-ESI-TOF MS together with the MS/MS information provided by the ion trap/reTOF MS elucidates posttranslational modifications, sequence changes, truncations, and isoforms that may otherwise go undetected when standard MALDI-MS peptide fingerprinting is used. This capability is critical in the analysis of human cancer cells where large numbers of expressed proteins are modified, and these modifications may play an important role in the cancer process.

A comparison of drug-treated and untreated HCT-116 human colon adenocarcinoma cells using a 2-D liquid separation mapping method based upon chromatofocusing PI fractionation

A multidimensional chromatographic 2-D liquid-phase separation method has been developed for differential display of proteins from cell lysates and applied to a comparison of protein expression between Peninsularinone-treated and untreated HCT-116 human colon adenocarcinoma cells. The method involves fractionation according to pI using chromatofocusing with analytical columns in the first dimension followed by separation of the proteins in each pI fraction using nonporous reversed-phase HPLC. A 2-D map of the protein content of each cell line based upon pI versus hydrophobicity as detected by UV absorption was generated and a differential display map indicating the presence of up- or downregulated proteins displayed using ProteoVue and DeltaVue software. Using this method, > 1000 protein bands could be detected in 0.2 pH fractions over a pH range of 4-7. In addition, the liquid eluent from the separation was directed on-line into an electrospray TOF-MS to obtain an accurate molecular weight of the intact proteins. An accurate molecular weight together with the peptide map was used to obtain protein identification using database searching. The method has been shown to have high reproducibility for quantitative differential display analysis of interlysate comparisons, generation of accurate protein identifications, and ease of data interpretation. It has been used herein to identify proteins that change as a function of drug treatment. The relative simplicity of the current procedure and the potential for full automation will make this technique an essential tool in future proteomic studies.

Boundary between Protein and Peptide Shown by Their Chromatographic Behavior

It has previously been pointed out that two different mechanisms exist in the reversed-phase (RP) HPLC of polypeptides, including proteins. We systematically investigated the separation of various peptides and proteins over a wide range of molecular weight using a nonporous octadecylsilyl (ODS) silica-gel column to provide a precise explanation for the separation mechanism of polypeptides, including proteins in RP-HPLC. As a result, we clarified that a critical point between a typical reversed-phase partition mode applicable to small peptides (molecular weight < 3000) and a characteristic elution mode applicable to proteins is in the vicinity of the molecular weight of 3500-4500. We also proposed a new concept, the "Transitional Desorption Mode", as a separation mechanism that can precisely explain the RP-LC separation of a wide range of polypeptides including proteins.

Two-dimensional liquid separations-mass mapping of proteins from human cancer cell lysates

A review of two-dimensional (2D) liquid separation methods used in our laboratory to map the protein content of human cancer cells is presented herein. The methods discussed include various means of fractionating proteins according to isoelectric point (pI) in the first dimension. The proteins in each pI fraction are subsequently separated using nonporous (NPS) reversed-phase high-performance liquid chromatography (RP-HPLC). The liquid eluent of the RP-HPLC separation is directed on-line into an electrospray ionization time-of-flight (ESI-TOF) mass spectrometer where an accurate value of the protein intact M(r) can be obtained. The result is a 2D map of pI versus M(r) analogous to 2D gel electrophoresis; however the highly accurate and reproducible M(r) serves as the basis for interlysate comparisons. In addition, the use of liquid separations allows for the collection of hundreds of purified proteins in the liquid phase for further analysis via peptide mass mapping using matrix assisted laser desorption ionization TOF MS. A description of the methodology used and its applications to analysis of several types of human cancer cell lines is described. The potential of the method for differential proteomic analysis for the identification of biomarkers of disease is discussed.

Rapid profiling of induced proteins in bacteria using MALDI-TOF mass spectrometric detection of nonporous RP HPLC-separated whole cell lysates

A method for rapid profiling of water-soluble proteins from whole cell lysates has been developed using matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOFMS) following separation by reversed-phase high-performance liquid chromatography (RP HPLC). Rapid separation of proteins from cell lysates was achieved using columns packed with C18 nonporous (NP) silica beads. Using this method, the whole cell lysate water-soluble proteins of E. coli were separated in under 15 min. A method using two columns in series at different temperatures was used in order to provide high loadability without loss of separation efficiency. The nonporous packing in the columns provided for high recovery. Eluting fractions were collected and analyzed by MALDI-TOFMS to determine the molecular weights and peptide maps of the proteins. These methods provided for the rapid screening and identification of proteins from E. coli where the response of E. coli to L-arabinose induction was studied. In this work, it is demonstrated that NP RP HPLC with MALDI-TOFMS detection may serve as a rapid means of detecting and identifying changes in bacterial protein expression due to external stimuli.

Protein separation using non-porous sorbents

This article overviews the development of non-porous sorbents having small particle diameters which have proven effective for rapid analysis and micropreparative separation of proteins by liquid chromatography. Much attention is given to the preparation and application of silica- and polystyrene-based non-porous packings for various chromatographic modes, especially affinity chromatography. Modeling works on the prediction and parameter estimation for the dynamics of protein adsorption using non-porous sorbents are reviewed and briefly described. To conclude this review, future prospects of the application of non-porous sorbents are also presented.

Reversed-phase HPLC separation of proteins on chemically bonded silica gel columns

Reversed-phase high-performance liquid chromatographic (RP-HPLC) separation of proteins on chemically bonded silica gel columns is described. Efficiency of nonporous alkylsilyl bonded silica gel is compared with that of a macroporous gel that has been widely used for the purpose. A comparative study of the separation under conventional and fast separation conditions is also given. The fast separation technique on the nonporous reversed-phase column has the advantage of improving the recovery of late-eluting hydrophobic and large proteins, such as ovalbumin and apoferritin.

Diol-bonded silica gel as a restricted access packing forming a binary-layered phase for direct injection of serum for the determination of drugs

Direct serum injection for drug determinations can be achieved on a diol-bonded silica gel as a restricted access packing. The diol-bonded phase, 3-(2,3-dihydroxypropoxy)propylsilylsilica, contains two different functions, a hydrophilic function at the tip of the single chemical bond and a hydrophobic function on the inside part of the bond to form a "binary-layered phase" on the support surface. Proteins, as large molecules, contact only the hydrophilic surface of the diol phase, and they are eluted at the solvent front based on size-exclusion chromatography. On the other hand, small molecules such as synthetic drugs are retained on the internal hydrophobic function and separate based on reversed-phase chromatography. Accordingly, the diol-bonded silica gel performs as a restricted access packing for direct serum injection for the determination of relatively hydrophobic drugs.

Rapid analysis of somatostatin in pharmaceutical preparations by HPLC with a micropellicular reversed-phase column

A rapid high-performance liquid chromatography method for the analysis of somatostatin in pharmaceutical preparations is described. A commercially available column packed with 2 microns spherical non-porous silica-based reversed-phase sorbent is used, along with a mobile phase consisting of acetonitrile and aqueous phosphoric acid, adjusted to pH 2.8 with sodium hydroxide. The effect of the organic modifier content and column temperature on the retention behaviour of somatostatin is reported. The method is found to be highly selective and specific, as indicated by the baseline separation of a mixture containing somatostatin and two analogue peptides, which differ from the analyte for one and two amino acids, respectively. Down to 10 ng of somatostatin can be detected and the detector response is linear over the concentration range from 4.14 to 20.75 micrograms ml-1. The application of this method to two commercial pharmaceutical formulations of somatostatin is found to give a mean percentage recovery from each of the two commercial samples, subjected to multiple injection analysis (n = 5), of 100.9% with a RSD of 0.92%, and 102.6% with a RSD of 1.56%, respectively.

Chromatography in analytical biotechnology

Recent advances in biochromatography have focused on improvements in the design of stationary supports for liquid chromatography. During the past year, the innovative use of columns packed with small non-porous particles has significantly improved the efficiency of chromatographic separations. Bioseparations that previously took hours are now possible in only a few minutes.